The goal of this research proposal is to understand the role of various endocytic trafficking events in the regulation of Notch and Wingless signaling. Focusing on the Drosophila wing, where the pathways interact, I have performed preliminary studies using Hrs, a protein implicated in multivesicular body formation. I have found genetic interactions with signaling members, as well as changes in protein levels and localization, suggestive of a role in signal regulation. Here, I plan to tease apart endocytosis by analyzing the importance of each step of trafficking on Notch and Wingless signaling regulation. I will perform a detailed study of the subcellular localization of signaling members by microscopy. Then, using genetic tools that modulate vesicle trafficking events, I will characterize changes in protein subcellular localization and analyze the resultant wing phenotypes. Finally, I will investigate the role of endocytosis in establishing the Wingless morphogen gradient. Together, these studies will contribute to our understanding of Notch and Wingless signaling and provide insight into how these pathways control cell proliferation and cell fate determination.